Add port to firewalld for external access

The following command will list the current firewall rules:

firewall-cmd --list-all

To add a new rule, issue the following command:

firewall-cmd --zone=public --permanent --add-port=443/tcp

Next, reload firewalld:

firewall-cmd --reload

List the rules again to confirm:

firewall-cmd --list-all

RE: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/security_guide/sec-viewing_current_status_and_settings_of_firewalld